My boyfriend looks raging mad every time he see's the girl who "led him on" ?

So he liked a girl who led him on very strongly... he deeply likes me (according to everyone) but he stil looks deeply hurt and angry when he sees the girl he used to like.. especially since her and i are close friends.. he also told me he hopes i am not listening to anything she is saying about him. My boyfriend and i are inseperable best friends... but still... what should I do and why is he like this?

Thanks for understanding... it is... very much. But she adores me and is so happy with her own fiance... she confides in me and somehow, we just became really close.. so yeah... awkward as, because her and my boyfriend are both important people in my life :(